(1) Field of the Invention
The present invention relates to the delivery of charge material to the interior of a shaft furnace. More specifically, this invention is directed to methods of and apparatus for reducing component wear is bell-less charging installations for blast furnaces through the exercise of control over the trajectory of material delivered from storage hoppers to a charge distribution chute located within the furnace. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
Recent developments in the field of high capacity blast furnaces have resulted in the imposition of increasingly exacting demands on the charging devices employed in such furnaces. It is known, for example, that furnace efficiency can be maximized by insuring that the throat gases pass through the furnace charge in an optimum manner. The optimum gas flow, in turn, may be achieved only through exercising close control over the distribution of the furnace charge material on the hearth. The configuration assumed by the charge or burden on the furnace hearth, in turn, depends directly on the charging device employed. Two basic types of charging devices are presently known in the art. The first, which has been in use for many years, employs two superimposed bells. When employing such bell-type charging devices it is inherently impossible to distribute the charge in an even and uniform manner over the surface of the furnace hearth; the charge configuration resulting from use of a bell-type charging device having a characteristic M curve. The second category of charging device, which is achieving increased acceptance and use, is a bell-less charging system which includes a rotatable and angularly adjustable spout located within the furnace. The bell-less charging system is described in U.S. Pat. No. 3,693,812, and improvements thereto are disclosed in U.S. Pat. Nos. 3,814,403 and 3,880,302. The three aforementioned U.S. patents are all assigned to the assignee of the present invention, and reference is made thereto for details of the features disclosed in said patents.
In the apparatus of U.S. Pat. No. 3,693,812, the furnace charge material or burden is stored in two or more intermediate storage bins or hoppers and is supplied to the distribution chute in controlled quantities, through the use of a metering device, via a discharge funnel and a central feed channel. In the manner known in the art, the storage hoppers are operated in accordance with a predetermined cycle; i.e., while one of the hoppers is being filled with charge material the other will be discharging its contents into the discharge funnel from which the material flows through the central feed channel to the distribution chute and thence on to the furnace hearth. The central feed channel is located vertically above the material receiving end of the rotatable distribution chute and coaxially of the mechanism for driving the distribution chute. The discharge funnel, which is of generally frustoconical shape, is vertically above and coaxial with the feed channel; the smaller diameter end of the discharge funnel facing the upstream end of the central feed channel. Referring to U.S. Pat. No. 3,693,812, during charging of the furnace the charge material, for example ore or coke, will be alternately released from the hoppers 2, 2' and will be directed by the discharge funnel 12 into the fixed, vertical feed channel 13. The charge will then be guided by channel 13 onto the upper end of the rotatable and angularly adjustable chute 15. Due to its physical nature, the rapidly moving charge material will cause erosion of the walls of the discharge funnel and feed channel which are contacted thereby. The rate of wear of the sloped side walls of the discharge funnel and of the vertical wall of the feed channel is comparatively high since the material delivered from the intermediate storage hoppers to the furnace generally falls over the same trajectory and thus always comes in contact with the same surface areas which, accordingly, experience constant wear.